1. Field of the Invention
The present invention relates to security windows, and more particularly relates to security windows having electrically operated shutters therein.
2. Description of Related Art
Multilayered security structures are known. See, for example, Molari, Jr., U.S. Pat. No. 4,027,072, which discloses laminates of glass and polycarbonate block copolymers. While such laminates are suitable for use in security applications and exhibit good energy absorption, clarity, strength, integrity and penetration resistance, these prior laminates do not, in and of themselves, provide security officers with the option of electrically controlling the viewability therethrough.
Electrically controlled optical shutters are known. See, for example, Ferguson, U.S. Pat. No. 4,556,289, which discloses an optical shutter and discloses employing a polycarbonate support medium. Electrically controlled optical shutters have applications in visual displays, such as billboards, or for controlling the passage of light from one area to another.
Laminates of light valves are known. Presently, laminates of light valve film and glass are available, but the resulting laminates are fragile and are generally unsuitable for exterior use, since the light valve film is subject to ultraviolet degradation.
An object of the present invention is to laminate a light valve film with a thick polycarbonate sheet, thus resulting in a less fragile laminate than those commercially available.
Another object of the present invention is to provide an impact resistant laminate of a light valve film and a UV stabilized polycarbonate sheet that would reduce the ultraviolet radiation degradation of the light valve film. In addition, an object of the present invention is to provide a suitable adhesive layer for the polycarbonate sheet and the light valve film.
A further object of the present invention is to provide a security window which will allow prison staff to quickly and effectively control viewability through the window.